The invention relates to a device for and a method of detecting an end point of electro-plating, which is necessary, for instance, for producing orifice sheets.
Orifice sheets as known for instance from inkjet printheads are usually fabricated by one of the following two different methods, which are generally known. The first method is a mechanical method and the second method is an epitaxial growth method.
In the mechanical method, as described in U.S. Pat. No. 5,685,074, a thin sheet or tape is fabricated by any common sheet or tape fabrication process. This thin sheet or tape is put onto an anvil and a punching device punches bores at desired positions through the thin sheet or tape. Afterwards, the thin sheet or tape comprising bores at desired positions is cut to the desired form and size, yielding the orifice sheets. Another way of mechanically producing orifice sheets is to cut the thin sheet or tape first, yielding small formed sheets. Then, these small formed sheets are put onto an anvil and a punching device punches bores at desired positions through the small formed sheets, yielding the orifice sheets. This mechanical method bears the disadvantage, that the position of the bores in the orifice sheet is not reproducible to each other as well as to the borders of the orifice sheet. Additionally, the compound as well as the thickness of different thin sheets or tapes can easily vary between different cycles of production during any common sheet or tape fabrication process or between different common sheet or tape fabrication processes.
In the epitaxial growth method usually a vapor deposition process, e.g., a chemical vapor deposition (CVD) process, a plasma enhanced chemical vapor deposition (PECVD) process, a molecular beam epitaxy (MBE) process, and the like, or an electro-plating process is employed for fabricating an orifice sheet. Desired material is grown up epitaxially on a substrate in both different production processes, thereby forming an orifice sheet layer on the substrate, which is finally removed from the substrate for yielding the orifice sheet. The above mentioned vapor deposition processes can make use of masks for producing bores during growing up the orifice sheet. The use of a mask, however, has the disadvantage, that the diameters as well as the position of the bores are not exactly controllable.
The best results during producing orifice sheets according to the state of the art are delivered by an electro-plating process. This process usually makes use of a mandrel having a substrate and a thin conductive layer on the substrate. Such a mandrel is known from U.S. Pat. No. 4,773,971. There is further disclosed, that the conductive layer is etched to form a mold for the orifice sheets, which should be manufactured. This mold is electro-plated with a desired orifice sheet material. The final orifice sheet is removed from the mold after electro-plating. The electro-plating process makes use of a constant current or a constant voltage, respectively, and an adjusted electro-plating time to achieve the desired thickness of the final orifice sheet and to achieve the desired bore size or bore diameter, respectively. Due to the variability of the electro-plating rates between different cycles of electro-plating as well as between different electro-plating apparatus, time consuming and costly pre-control electro-plating runs are required to estimate the electro-plating time, which is required for each electro-plating apparatus at the beginning of each cycle of electro-plating.
One main aspect of the invention is to provide a possibility to detect the desired end point of electro-plating, which is universally applicable, i.e., independent from variations of the electro-plating rates between different cycles of electro-plating as well as between different electro-plating apparatus.
A device for detecting an end point of electro-plating and a method thereof according to the independent claims of the invention avoids time consuming and costly pre-control electro-plating runs.
A device for detecting an end point of electro-plating according to the invention comprises a mandrel having a substrate and a patterned conductive layer on the substrate, an insulation region, and a sensor. The patterned conductive layer comprises a main conductive area and an insulated conductive area. The insulated conductive area is electrically insulated from the main conductive area by the interposed insulation region. The sensor is electrically connected to the insulated conductive area for detecting a signal which indicates the end point of electro-plating.
A method of detecting an end point of electro-plating according to the invention provides above all a mandrel having a conductive layer on a substrate. Then, an insulation region is provided interposed on the substrate between two areas of the conductive layer, which yields a main conductive area and an insulated conductive area. Afterwards, a sensor is electrically connected to the insulated conductive area. Subsequently, a layer of conductive material is electro-plated on the main conductive area to cross the insulation region. Finally, a signal is detected by the sensor when the electro-plated layer of conductive material contacts the insulated conductive area, i.e. an electrical shortcut occurs between the main conductive area and the insulated conductive area, which indicates the end point of electro-plating.
One advantage of the invention over the prior art is, that time can be saved in every production cycle by eliminating the need of pre-control electro-plating runs. Another advantage of the invention is that the thickness of the electro-plated conductive material, the bore shape, the bore size and the bore diameter can be precisely adjusted, either singly or in any desired combination with one another, by means of patterning the insulation region with a desired depth, width and shape.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference numbers.